Just a few ideas:
A good first aid kit - check through that everything is up to date. Old bandaids dont stick. Someone on this site sells really good kits.
In the food department, we cook some meals in advance, put then in a plastic freezer bag, then in a chinese food take-away style container and freeze them at home. We then leave the container behind when we go camping but your meal is neatly frozen into a rectangle - easy, compact stacking in your portable fridge/freezer. These meals are good for the first night in or when you really cant be bothered cooking. Also means you are not carting home a pile of empty plastic containers that take up room.
Cup-a-soups are really easy, quick lunches as an alternative to sandwiches/rolls
Herbs and spices - we use one of the those plastic seven-day pill dispensers that you can buy at most chemists and some supermarkets. Means you can just take a little bit of everything with no glass containers.
Find plastic containers that are all the same shape for flour, sugar, cereal etc. Then they will stack better, store better, not break and are lighter. Write on the lids what is in them so you dont have to pull everything out of the drawer/box to find the one you want.
Alfoil and re-sealable plastic bags
If you dont like grotty tea-towells
(and dont plan on doing any clothes washing), buy a couple of chamois (like the ones you dry your car with). They do great at drying up dishes then you can give them a good rinse and let them dry out.
A head torch for everyone (they are
) and spare batteries (they always seem to go flat at the worst possible time)
I am sure others will add to this list. If you have an iPhone/iPad, there are some good "list" apps where you can create custom check-lists to make sure you have everything and you can add to it as you think of things. Cant recall the name of it, but someone will reply.